Bromine-based flame retardants, antimony trioxide, and the like have been used in large quantities in insulator materials for conventional heat-resistant low-voltage electrical wires for motor vehicles. However, such insulator materials release toxic gases, e.g., halogen gases, during a vehicle fire or incineration disposal to pose an environmental problem. Furthermore, sufficient heat resistance is obtained only when the covering layer formed by extrusion molding is crosslinked by irradiation with electron beams. Production of the conventional heat-resistant electrical wires requires an expensive electron beam irradiator and necessitates an electron beam irradiation step, resulting in low productivity.
Under these circumstances, a non-crosslinking type resin composition for heat-resistant electrical wires has been developed in recent years. This resin composition includes a poly(phenylene ether) material which has excellent heat resistance and attains high flame retardancy even in case of halogen-free, i.e., having no halogen (patent document 1).
A technique in which a styrene-based elastomer is incorporated as a compatibilizing agent for polypropylene and poly(phenylene ether) is disclosed (patent document 2).